1. Field of the Invention
The present invention relates to a gas discharge tube. More particularly, the present invention relates to an elongated gas discharge tube having a diameter of about 0.5 to 5 mm.
2. Description of the Related Art
In conventional elongated gas display tubes, a phosphor (fluorescent) layer is formed within the tube by introducing a phosphor slurry (coating solution containing a phosphor powder) into the tube, coating the slurry on an internal surface of the tube, and firing the slurry to burn out organic components of the slurry.
Firing is easily performed if the tube has a diameter (4 mm or more) large enough to have a low resistance to introduction of the air into the tube (high conductance).
Meanwhile, display devices for displaying desired images are known in which a plurality of elongated gas discharge tubes are arranged parallel to each other. Such display devices employ elongated gas discharge tubes of a diameter of 0.5 to 5 mm.
Gas discharge tubes of a diameter of 2 mm or less as mentioned above, when a phosphor layer is formed within it, have difficulty in completely burning out organic components even if a phosphor slurry coated on an internal surface of the tube is fired because of a low conductance of air flow through the tube.
Due to this, a discharge gas enclosed in the tube in a later step is contaminated by residues produced from the organic substances in the firing, so that the discharge characteristics of the gas discharge tube are adversely affected. This problem frequently occurs especially with tubes whose length exceeds 300 mm.
The present invention has been made under the above circumstances, and provides a gas discharge tube comprising a supporting member independent of a tubular vessel, wherein a phosphor layer is formed on the supporting member. The present invention aims that it is possible to form the phosphor layer easily and perform firing outside the tube for forming the phosphor layer, so that a discharge gas is prevented from being contaminated by residues produced after a phosphor slurry is fired. This results in stabilized discharge characteristics and improved luminous efficiency of the gas discharge tube.
A gas discharge tube according to the present invention is constructed so that a phosphor layer is formed on a supporting member independent of a tubular vessel of the gas discharge tube and the supporting member is disposed within a discharge space by inserting the supporting member inside the tubular vessel.
According to the present invention, since the phosphor layer is formed on the supporting member independent of the tubular vessel of the gas discharge tube, it is possible to form a phosphor layer of a uniform thickness easily and perform firing outside the tubular vessel of the gas discharge tube for forming the phosphor layer. This makes it possible to prevent a discharge gas being contaminated by residues produced after a phosphor slurry is fired.